Recently, due to economic benefits of LED providing a semi-permanent life with a high energy efficiency and brightness relative to conventional light sources such as an incandescent lamp, a fluorescent light, a halogen lamp, etc. used for a lighting apparatus and the improvement of optical characteristics of white LED enabled by the distribution of blue LED, the dominance of white LED over conventional light sources such as an incandescent lamp, a fluorescent light, a halogen lamps, etc. is growing.
Due to the insufficient intensity of light, a single LED diode alone cannot fulfil the normal usage of LED lighting. Thus, in general, multiple diodes are distributed within an LED array working as a surface light source to be embodied in an LED light apparatus. However, LED light has a strong characteristic of straight progression which makes each diode in the array independently visible, wherein incurs peripheral light leakage creating glare problems and eventually resulting discomfort to viewers.
To solve such problems, it is suggested to use a light reflector of the conventional lighting apparatus to set a limit on viewing angles of LED lighting. Typical related art documents are as follows.
Patent Document 1, the title of ‘High Illumination Reflector for LED Lighting Unit’, discloses a device that utilizes a high illumination reflector to reflect light emitted from LED and direct it facing forward in order to control viewing angles for the purpose of sending light to the desired direction only, so as to keep LED light from directly emitting toward a viewer's eye and thus prevent glare or blurred vision.
Patent Document 2, the title of ‘Save Electricity Type LED Lighting Device’, discloses an anti-glare device that utilizes a reflector to limit viewing angles for light emitted from LED.
Patent Document 3, the title of ‘LED Fluorescent Lamp Apparatus’, discloses a device that utilizes a reflector fixed on an LED fluorescent lighting apparatus to improve brightness and prevent glare and heat.
Patent Document 4, the title of ‘LED Plane Light’, discloses a lighting apparatus that utilizes a reflector mounted at the upper part of the PCB equipped with an LED surface light source in order to converge light in the desired direction for the higher efficiency.
Patent Document 5, the title of ‘LED Lighting Lamp’, discloses a device that utilizes a reflector with various angles in order to focus light emitted from LED diodes on the desired direction.
Patent Document 1 to 5 mentioned herein utilized a reflector of conventional fluorescent lights in order to limit viewing angles of a lighting apparatus and prevent glare. Despite differences in the specific forms of light source, they share a common element of adopting a reflector from conventional lighting apparatuses.
However, as described above, LED light source has a prominent attribute of straight progression which is incapable of removing independent visibility of every single LED diode. In order to solve this problem, there introduced a technology to diffuse light emitted from LED which means to distribute light-diffusing members on LED to prevent the independent visibility of each LED diode.
Patent Document 6, the title of ‘Opening and Shutting Structure of an electric lamp’, discloses a device in which a light diffusion cover is installed on the LED module to enable light emitted from the LED module to diffuse during the progress.
In spite of merits disclosed in Patent Document 6, wherein a light-diffusing member prevents each LED diode from being independently visible, the diffusion of light widens viewing angles and eventually intensifies glare problem. Accordingly, there introduced another technology that is to place an optical viewing angle adjusting member on a light-diffusing member to converge diffused light.
Patent Document 7, the title of ‘Front Plate for Light Lamp and Lighting Apparatus Having the Same’, discloses a device in which light emitted from a light source is diffused in a light-diffusing layer and condensed by patterns formed in a structural layer as it penetrates the structural layer.
Nevertheless, as described in Patent Document 7, wherein a light-diffusing member (light-diffusing layer) and an optical viewing angle adjusting member (structural layer) are condensed, the index matching takes place between the light-diffusing member and the optical viewing angle adjusting member. This sharply diminished the attribute of the optical viewing angle adjusting member while drastically augmenting the attribute of the light-diffusing member in the lower part and exposed the necessity of the structure that allows the light-diffusing member and the optical viewing angle adjusting member to function independently. In addition, because a light-diffusing member and an optical viewing angle adjusting member have been produced separately and then condensed so far, each of them was bent by gravity thus bound to be thicker than necessary (1.5 mm or less). Consequently, the overall thickness of the thickened optical plate for lighting became problematic.